Stills is an incredibly soft and finesse player but no doubt very skilled with his speed trade. He should definitely have more than 25 catches and only a few hundred yards with 3 games left in the season.
You're not far off but he has 32 catches, 504 yards and 6 TDs. With three more games I imagine he gets close to 50 catches, another 200 yards and at least 2 more TDs. That's not terrible considering all of the injury and play calling nonsense this team went through.
The good news is if teams really try to shut him down it will allow Tannehill to use Amendola and Drake to move the ball, and both have been quite effective catching passes.